1. Field of the Invention
The present invention relates to substrate structures and semiconductor packages, and, more particularly, to a substrate structure and a semiconductor package for flip-chip packaging.
2. Description of Related Art
Increased miniaturization, multi-function and high performance of electronic products require circuit boards or packaging substrates to have fine lines/fine pitches. Compared with a wire-bonding semiconductor package, a flip-chip semiconductor package has increased number of connections and becomes more popular.
FIG. 1 is a schematic top view of a conventional flip-chip packaging substrate. A plurality of circuits 11 are formed on the packaging substrate and an electrical contact 111 is formed at one end of each of the circuits 11 for electrical connection with a semiconductor chip. The electrical contact 111 is smaller in width than the circuit 11. As such, the density of the circuits 11 is limited by the size of the electrical contacts 111, thus adversely affecting the fabrication of high-density circuits and limiting the electrical performance of the semiconductor package.
To overcome the above-described drawbacks, a ball on trace (BOT) technology has been developed. Referring to FIG. 2, a portion of a circuit 21 serves as an electrical contact so as to eliminate the need to form an electrical contact and consequently eliminate the limitation posed by the electrical contact on the circuit density. Generally, the portion of the circuit 21 serving as the electrical contact is wider than the other portion so as to strengthen the flip-chip bonding and increase the product reliability. However, the wider portion of the circuit 21 limits the circuit density of the packaging substrate 2.
Further, increased circuit density of packages and increased number of electrode pads of semiconductor chips result in reduced size of solder balls 22, thus reducing the bonding strength between the solder balls 22 and the circuits 21 and hence reducing the product reliability.
Therefore, how to overcome the above-described drawbacks has become critical.